Lateral Movement of Auxin in Phototropism

Abstract

Lateral movement of IAA-l-l4c in corn [Zea mays] coleoptiles was measured as radioactivity moving laterally following unilateral application of the auxin. The data suggest that there is an endogenous lateral movement of auxin, and that phototropic stimulation of the coleoptile depresses lateral movement towards the light and enhances lateral movement away from the light. The lateral movement was found to be principally as IAA. In experiments using sunflower [Helianthus annuus 1 hypocotyl sections, evidence is also presented to support the suggestion that lateral redistribution of auxin may be effected by a deflection of auxin around a barrier to basipetal transport.